Pouring tubes are well known for use in metal casting processes. They are arranged vertically and a stream of molten metal is poured through them. The function of the tube is to protect the stream of molten metal from the surrounding atmosphere. Normally, the stream flows though the tube without touching its sides, but the tube must be able to withstand being full of molten metal in certain circumstances.
In continuous casting, molten metal, most often steel, is fed into a continuous casting mould from a constant head vessel known as a tundish. Molten metal is fed into the tundish from successive ladles of molten metal. The quality of the continuously cast metal strand can be adversely affected by oxide and other non-metallic inclusions, and it is found that the incidence of such inclusions may be reduced if the molten metal is protected from oxidation by the surrounding atmosphere by surrounding the stream of metal with a tube. Simply surrounding the molten metal stream with a tube gives some improvement, but it is highly preferred to inject into the tube an inert atmosphere e.g. to inject nitrogen or argon into the tube, so that the molten metal stream is surrounded by an inert atmosphere as it passes either from ladle to tundish or from tundish to continuous casting mould.
Known pouring tubes (French Patent Specification No. 2333599) consist of a tube of refractory heat insulating material encased in a thin sheet metal casing e.g. of mild steel. Such tubes are expensive to fabricate, requiring the separate manufacture of the refractory heat insulating material member and of a sheet metal casing therefor and the assembly together of the two.
We have now found that effective pouring tubes may be made by a substantially simpler process without any loss of effectiveness.